Page 117 - Threading_Handbook

Radial Infeed

With radial infeed, the thread is machined simultaneously and symmetrically with two cutting
edges. In this processing method, the chip tends to bend on either side of the cutting
edge against each other, as a result of the chip winding process, and the removal of the
chip becomes more difficult. This method creates large forces on the cutting edge and THREAD TURNING
warming of cutting edges which causes short tool life and limits the possible depth of cut.
Cutter wear is uniform on both sides of the cutting edge. Radial infeed is acceptable in the
production of fine pitch threading or finish passes, to ensure threading profile accuracy.

Flank Infeed

With the flank infeed method, the cutting edge moves parallel to one of the sides of the
threading profile. The threading is produced mainly by one side of the cutting edge. The
chips are cut off with one cutting edge of the cutter, which improves chip evacuation relative
to the radial method, and therefore the cutting depth per each pass can be bigger. Using
the flank method provides better heat dissipation, which improves tool life but causes
uneven wear of the cutter’s cutting edges. As cutting is done mainly with one cutting edge,
friction is created between the cutting edge and the side of the threading profile, which
causes poor surface quality and possible vibration.

Modified Flank Infeed (Recommended)

Modified flank infeed is very similar to the flank infeed method, but the angle between the
cutting edge to the side of the threading profile can be between 0.5° to 5°.
In this method, all the advantages of flank infeed are retained while the disadvantages
caused from friction between the cutting edge and the side of the threading profile
are prevented. Modified flank infeed is the recommended method for all thread turning
operations and is suitable for all insert types.

Alternating Flank Infeed

In this method, cutting edges work alternately, i.e. each time the cut is performed by another
side of the cutting edge. This method can significantly increase tool life due to two cutting
edges taking part in the threading production. Constant changing of the chip evacuation
direction can result in poor surface quality. This method is usually used for very large pitches
and for threading forms such as Acme and Trapeze.

117